Objective: To clarify the relationship of serum inhibitors of corneal collagenase to ulceration. Collagenase has been implicated in the pathoetiology of corneal ulceration in various disease states in humans and in ulceration of the alkaliburned and Herpes-infected rabbit cornea. Although the factors which control collagenase activity in the injured cornea are unknown, previous studies in our laboratory have indicated that whole serum and the antiproteases, alpha 1-Antitrypsin and alpha 2-Macroglobulin inhibit corneal collagenases. It is our intention to use methods of measuring enzyme inhibition and immunochemical techniques to attempt to determine if the antiproteases play a significant role in controlling collagenase activity in the injured cornea. The demonstration of such a role would support the therapeutic use of serum and serum antiproteases and other natural protease inhibitors in cases of ulceration. In the proposed studies, enzyme preparations from the human cornea and from the ulcerating rabbit cornea, which serves as a model system, will be employed. Specifically, we intend to: 1. determine the relative efficacies of the serum antiproteases in inhibiting autologous corneal collagenase in order to assess the possible in vivo signficance of those proteins. 2. determine the relationship between corneal ulceration and the levels of collagenase, antiproteases, and collagenase-antiprotease complexes in tears that bathe the ulcerating cornea.